A basilisk is a Slayer monster that requires a Slayer level of 40 to kill and can be found at the Fremennik Slayer Dungeon. Like cockatrices, players must equip a mirror shield when fighting these monsters. Players require a Defence level of 20 in order to receive basilisks as a slayer assignment, as a Defence level of 20 is required to wield the shield. Basilisks have a below average accuracy for their level, but have high Defence.

Without the mirror shield, the player's stats will be greatly reduced. Protect from Melee prayer can be used, but the stats will still be lowered.

These can be safespotted from the southern entrance to their area in the slayer cave, by using the south-east wall to stop their movement or by using the rocks on either side of the room. Note that players cannot set up a dwarf multicannon within the dungeon.